Not receiving emails on Comcast IMAP email accout

My Comcast IMAP email account is not receiving emails my husband is sending from his .mac email account.  His .mac email account is showing the emails successfully sent however they're not showing up on my Comcast account.  I've had a number of issues with not receiving emails on both of my Comcast accounts.  My husband was just using his .mac account to try to diagnose the problems but they're not showing up on my Comcast email account.  Any help or guidance would be appreciated.  I should also mention that the emails are not coming through are not limited to things from the .mac domain.  I've had missing emails also from a number of other domains although I don't have the particulars about those other domains.